# [Gmsh] Problem of Conformal Meshing at Volume boundaries

Patrick Tsui pcptsui at gmail.com
Mon Aug 3 18:13:03 CEST 2020

```Dear All,

I am having trouble getting conformal meshing at boundaries of volumes. I
tried a good number of suggestions found online but failed. For the simple
codes tested (listed below and attached), 104 errors appeared. Gmsh 4.7.0
on Ubuntu 19.10 were used. Any help would be highly appreciated.

// Code begins
------------------------------------------------------------------------

mm2m = 0.001;
i2m = 0.0254;
Geometry.AutoCoherence = 1;
Mesh.CharacteristicLengthMin = 0.125*i2m;
Mesh.CharacteristicLengthMax = 0.250*i2m;
Geometry.Tolerance = 0.01*mm2m;
lc  = 0.125*i2m;

a  = 2.0 * i2m;
p1=newp; Point(p1) = { a, 0.0,  a, lc};
p2=newp; Point(p2) = {-a, 0.0,  a, lc};
p3=newp; Point(p3) = {-a, 0.0, -a, lc};
p4=newp; Point(p4) = { a, 0.0, -a, lc};
l1=newl; Line(l1) = {p1, p2};
l2=newl; Line(l2) = {p2, p3};
l3=newl; Line(l3) = {p3, p4};
l4=newl; Line(l4) = {p4, p1};
ll1=newll; Curve Loop(ll1) = {l1, l2, l3, l4};
s1=news; Plane Surface(s1)={ll1};
hh = 0.5*i2m;
id[] = Extrude {0,hh,0} { Surface{s1}; Layers{ 1 }; Recombine; };
v1 = id[1];

p5=newp; Point(p5) = { a/2, 0.0,  a/2, lc};
p6=newp; Point(p6) = {-a/2, 0.0,  a/2, lc};
p7=newp; Point(p7) = {-a/2, 0.0, -a/2, lc};
p8=newp; Point(p8) = { a/2, 0.0, -a/2, lc};
l5=newl; Line(l5) = {p5, p6};
l6=newl; Line(l6) = {p6, p7};
l7=newl; Line(l7) = {p7, p8};
l8=newl; Line(l8) = {p8, p5};
Point {p5,p6,p7,p8} In Surface{s1};
Line {l5,l6,l7,l8} In Surface{s1};

ll2=newll; Curve Loop(ll2) = {l5, l6, l7, l8};
s2=news; Plane Surface(s2)={ll2};
id[] = Extrude {0,-hh,0} { Surface{s2}; Layers{ 1 }; Recombine; };
v2 = id[1];

Surface {s2} In Volume{v1};

v() = BooleanFragments{ Volume{v1}; Delete;}{ Volume{v2}; Delete;};
n=#v();
For i In {0:n-1}
Printf("v(%g) = %g",i,v(i));
EndFor

Mesh 3;
Coherence Mesh;

// Code ends
------------------------------------------------------------------------

Sincerely,

PT
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```